Now, toji is used by stressed-out Japanese workers to rejuvenate. People see onsen not so much as a part of their everyday lives but as a means of escape from them.

“Now, many people visit onsen to relax and take advantage of the healing benefits that they offer, and they enjoy it, not just heal and recover,” says Hirokazu Nunoyama, secretary-general of the Japanese Spa Association.

Onsen come in all shapes and sizes. Some, like Dogo, are housed in buildings hundreds of years old. Others are outside and/or part of upscale resorts. Expect to pay up to $20 for the bathing experience itself, and considerably more if you’re staying overnight at a ryokan (traditional Japanese inn).

“Good onsen should have really hot water that doesn’t smell like chlorine, and in my opinion, should be off the beaten path or should have historical or cultural significance,” says Ray Bartlett of OnsenJapan.net.

Japanese often choose an onsen based on the type of water. Some women tend to seek out waters rich in sodium bicarbonate to help make their skin soft. The muddy waters of iron-rich hot springs are said to be good for anemia sufferers and for helping the body retain heat. There are even waters containing hydrogen sulfide, which is said to be effective for softening the skin and for curing acne.

For the uninitiated, the first onsen visit can be intimidating. But it actually becomes a relaxing experience once a few simple rules are understood … and the fear of being naked in front of strangers abates.

After getting undressed, it’s time to bathe. Usually there is a line of stools and bowls in front of water faucets. You must wash yourself thoroughly with soap and water from head to toe. This is not negotiable. The biggest onsen sin is not washing and rinsing yourself properly.